/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.client;

import java.io.IOException;
import java.io.InputStream;
import java.io.PushbackInputStream;

import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.client.ClientHttpResponse;
import org.springframework.lang.Nullable;

/**
 * Implementation of {@link ClientHttpResponse} that can not only check if
 * the response has a message body, but also if its length is 0 (i.e. empty)
 * by actually reading the input stream.
 *
 * @author Brian Clozel
 * @see <a href="http://tools.ietf.org/html/rfc7230#section-3.3.3">RFC 7230 Section 3.3.3</a>
 * @since 4.1.5
 */
class MessageBodyClientHttpResponseWrapper implements ClientHttpResponse {

    private final ClientHttpResponse response;

    @Nullable
    private PushbackInputStream pushbackInputStream;


    public MessageBodyClientHttpResponseWrapper(ClientHttpResponse response) throws IOException {
        this.response = response;
    }


    /**
     * Indicates whether the response has a message body.
     * <p>Implementation returns {@code false} for:
     * <ul>
     * <li>a response status of {@code 1XX}, {@code 204} or {@code 304}</li>
     * <li>a {@code Content-Length} header of {@code 0}</li>
     * </ul>
     *
     * @return {@code true} if the response has a message body, {@code false} otherwise
     * @throws IOException in case of I/O errors
     */
    public boolean hasMessageBody() throws IOException {
        HttpStatus status = HttpStatus.resolve(getRawStatusCode());
        if (status != null && (status.is1xxInformational() || status == HttpStatus.NO_CONTENT ||
                status == HttpStatus.NOT_MODIFIED)) {
            return false;
        }
        if (getHeaders().getContentLength() == 0) {
            return false;
        }
        return true;
    }

    /**
     * Indicates whether the response has an empty message body.
     * <p>Implementation tries to read the first bytes of the response stream:
     * <ul>
     * <li>if no bytes are available, the message body is empty</li>
     * <li>otherwise it is not empty and the stream is reset to its start for further reading</li>
     * </ul>
     *
     * @return {@code true} if the response has a zero-length message body, {@code false} otherwise
     * @throws IOException in case of I/O errors
     */
    public boolean hasEmptyMessageBody() throws IOException {
        InputStream body = this.response.getBody();
        if (body.markSupported()) {
            body.mark(1);
            if (body.read() == -1) {
                return true;
            } else {
                body.reset();
                return false;
            }
        } else {
            this.pushbackInputStream = new PushbackInputStream(body);
            int b = this.pushbackInputStream.read();
            if (b == -1) {
                return true;
            } else {
                this.pushbackInputStream.unread(b);
                return false;
            }
        }
    }


    @Override
    public HttpHeaders getHeaders() {
        return this.response.getHeaders();
    }

    @Override
    public InputStream getBody() throws IOException {
        return (this.pushbackInputStream != null ? this.pushbackInputStream : this.response.getBody());
    }

    @Override
    public HttpStatus getStatusCode() throws IOException {
        return this.response.getStatusCode();
    }

    @Override
    public int getRawStatusCode() throws IOException {
        return this.response.getRawStatusCode();
    }

    @Override
    public String getStatusText() throws IOException {
        return this.response.getStatusText();
    }

    @Override
    public void close() {
        this.response.close();
    }

}
